This invention relates to a process for the catalytic conversion of olefins to provide alcohols, ethers and their mixtures. More particularly, the invention relates to a process for the reaction of light olefins such as ethylene, propylene, butenes, pentenes, hexenes, heptenes, etc., and their mixtures, with water and/or lower alcohols to provide alcohol(s), ether(s) or mixtures thereof employing the acidic forms of certain synthetic porous crystalline materials, or zeolites, as catalysts. The alcohols, ethers and their mixtures are useful, inter alia, as high octane blending stocks for gasoline.
There is a need for an efficient catalytic process to manufacture alcohols and ethers from light olefins thereby augmenting the supply of high octane blending stocks for gasoline. Lower molecular weight alcohols and ethers such as isopropyl alcohol (IPA) and diisopropyl ether (DIPE) are in the gasoline boiling range and are known to have a high blending octane number. In addition, by-product propylene from which IPA and DIPE can be made is usually available in a fuels refinery. The petrochemicals industry also produces mixtures of light olefin streams in the C.sub.2 to C.sub.7 molecular weight range and the conversion of such streams or fractions thereof to alcohols and/or ethers can also provide products useful as solvents and as blending stocks for gasoline.
The catalytic hydration of olefins to provide alcohols and/or ethers is a well-established art and is of significant commercial importance. Representative olefin hydration processes are disclosed in U.S. Pat. Nos. 2,162,913; 2,477,380; 2,797,247; 3,798,097; 2,805,260; 2,830,090; 2,861,045; 2,891,999; 3,006,970; 3,198,752; 3,810,849; and, 3,989,762, among others.
Olefin hydration employing zeolite catalysts is known. As disclosed in U.S. Pat. No. 4,214,107, lower olefins, in particular, propylene, are catalytically hydrated over a crystalline aluminosilicate zeolite catalyst having a silica to alumina ratio of at least 12 and a Constraint Index of from 1 to 12, e.g., ZSM-5 type zeolite, to provide the corresponding alcohol, essentially free of ether and hydrocarbon by-product.
According to U.S. Pat. No. 4,499,313, an olefin is hydrated to the corresponding alcohol in the presence of hydrogen-type mordenite or hydrogen-type zeolite Y, each having a silica-alumina molar ratio of from 20 to 500. The use of such a catalyst is said to result in higher yields of alcohol than olefin hydration processes which employ conventional solid acid catalysts. Use of the catalyst is said to offer the advantage over ion-exchange type olefin hydration catalysts of not being restricted by the hydration temperature.
U.S. Pat. No. 4,783,555 describes an olefin hydration process employing a medium pore zeolite as hydration catalyst. Specific catalysts mentioned are Theta-1, said to be preferred, ferrierite, ZSM-22, ZSM-23 and NU-10.
Japanese Laid-Open Patent Application No. 60-246335 discloses the hydration of branched olefins to alcohols in the presence of a zeolite having a silica to alumina ratio of above 10.
The catalyzed reaction of olefins with alcohols to provide ethers is another well known type of process.
As disclosed in U.S. Pat. No. 4,042,633, diisopropyl ether (DIPE) is prepared from isopropyl alcohol (IPA) employing montmorillonite clay catalysts, optionally in the presence of added propylene.
U S. Pat. No. 4,182,914 discloses the production of DIPE from IPA and propylene in a series of operations employing a strongly acidic cation exchange resin as catalyst.
In U.S. Pat. No. 4,334,890, a mixed C.sub.4 stream containing isobutylene is reacted with aqueous ethanol to form a mixture of ethyl tertiary butyl ether (ETBE) and tertiary butyl alcohol (TBA).
U.S. Pat. No. 4,418,219 discloses a process for preparing methyl tertiary butyl ether (MTBE) by reacting isobutylene and methanol in the presence of boron phosphate, blue tungsten oxide or a crystalline aluminosilicate zeolite having a silica to alumina mole ratio of at least 12:1 and a Constraint Index of from 1 to about 12 as catalyst.
As disclosed in U.S. Pat. No. 4,605,787, alkyl tertalkyl ethers such as MTBE and tertiary amyl methyl ether (TAME) are prepared by the reaction of a primary alcohol with an olefin having a double bond on a tertiary carbon atom employing as catalyst an acidic zeolite having a Constraint Index of from about 1 to 12, e.g., ZSM-5, ZSM-11, ZSM-12, ZSM-23 dealuminized zeolite Y and rare earth-exchanged zeolite Y.
U.S. Pat. No. 4,714,787 discloses the preparation of ethers by the catalytic reaction of linear monoolefins with primary or secondary alcohols employing, as catalyst, a zeolite having a pore size greater than 5 Angstroms, e.g., ZSM-5, zeolite Beta, zeolite X, zeolite Y, etc. Specifically, in connection with the reaction of propylene with methanol to provide methyl isoopropyl ether (MIPE), effluent from the reactor is separated into a MIPE fraction, useful as a gasoline blending component, with unreacted propylene, methanol, by-product dimethyl ether (DME) and water at up to one mole per mole of by-product DME, either individually or in combination, being recycled to the reactor.
In European Patent Application 55,045, an olefin is reacted with an alcohol to provide an ether, e.g., isobutene and methanol are reacted to provide MTBE, in the presence of an acidic zeolite such as zeolite Beta, ZSM-5, ZSM-8, ZSM-11, ZSM-12, ZSM-23, ZSM-35, ZSM-43 and ZSM-48, and others, as catalysts.
German Patent No. 133,661 describes the reaction of isobutene and methanol to provide a mixture of products including MTBE, butanol and isobutene dimer employing acidic zeolite Y as catalyst.
Japanese Laid-open Patent Application No. 59-25345 describes the reaction of a primary alcohol with a tertiary olefin in the presence of a zeolite having a silica to alumina mole ratio of at least 10 and the X-ray diffraction disclosed therein to provide a tertiary ether.
It is a common practice in zeolite catalyst manufacture to extrude the active zeolite component with an inorganic oxide binder component such as alumina. The binder serves as a matrix for the zeolite and facilitates the extrusion process resulting in a composite product possessing good mechanical strength. In many cases, the binder component contributes little to the observed catalytic activity and can be regarded as an inert diluent for the catalytically active zeolite component. However, it has now been discovered that the activity and selectivity of zeolite catalysts used in olefin hydration/etherification may be significantly influenced by the nature of the binders with which the zeolites are composited.